Positioning mechanism for pressure spring means in timepieces

ABSTRACT

THIS INVENTION CONCERNS WITH A POSITIONING MECHANISM FOR A PRESSURE SPRING PROVIDED IN A TIMEPIECE MOVEMENT FOR EXERTING AN AXIAL RESILIENT PRESSURE ONTO A SECOND HAND ARBOR SO AS TO SUBJECT THE LATER TO A FRICTIONAL ROTATION IN COMPENSATION OF UNAVOIDABLE BACKLASH EXISTING IN THE RELATED GEARING. THE POSITIONING MECHANISM IS PROVIDED WITH A POSITIONING STATIONARY PIN OR THE LIKE PRESSURE-LIMITING MEANS PROVIDED ON A MOUNTING PLATE OR AN UPPER PLATE WHICH MEANS IS SO DESIGNED AND ARRANGED THAT IT MECHANICALLY COOPERATES WITH THE FREE END OF SAID SPRING FOR LIMITING THE FREELY MOVABLE RANGE OF THE SPRING END, AS WELL AS THE PIVOTALLY MOVABLE RANGE THEREOF IN ADVANCE OF FITTING THE SECOND HAND ARBOR IN POSITION IN THE TIMEPIECE MOVEMENT, SAID PRESSURE-LIMITING MEANS BEING, HOWEVER, NORMALLY KEPT OUT OF MECHANICAL CONTACT WITH THE SPRING DURING THE REGULAR OPERATION OF THE TIME PIECE MOVEMENT.

Oct. 5, 1971 AKIRA TsuzuKl 3,609,901

POSITIONING MECHANISM FOR PRESSURE SPRING MEANS IN TIMBPIECES Filed Feb. 16, 1970 z sheets-shut 1 FIG.3

PRIOR ART Oct. 5, 1971 AKIRA TSUZUKI POSITIONING MECHANISM FOR PRESSURE. SPRING MEANS IN TIMEPIECES Filed Feb. 16. 1970 2 Sheets-Sheet 2 FIG.?

United States Patent Oflice 3,609,961 Patented Oct. 5, 1971 3,609,961 POSITIONING MECHANISM FOR PRESSURE SPRING MEANS IN TIMEPIECES Akira Tsuzuki, Tokyo, Japan, assignor to Citizen Watch Co., Ltd., Tokyo, Japan Filed Feb. 16, 1970, Ser. No. 11,604 Int. Cl. G04]: 19/02 US. Cl. 58-125 3 Claims ABSTRACT OF THE DISCLOSURE This invention concerns with a positioning mechanism for a pressure spring provided in a timepiece movement for exerting an axial resilient pressure onto a second hand arbor so as to subject the latter to a frictional, rotation in compensation of unavoidable backlash existing in the related gearing. The positioning mechanism is provided with a positioning stationary pin or the like pressure-limiting means provided on a mounting plate or an upper plate which means is so designed and arranged that it mechanically cooperates with the free end of said spring for limiting the freely movable range of the spring end, as well as the pivotally movable range thereof in advance of fitting the second hand arbor in position in the timepiece movement, said pressure-limiting means being, however, normally kept out of mechanical contact with the spring during the regular operation of the timepiece movement.

This invention relates to improvements in and relating to the positioning mechanism for pressure spring means employed in timepieces for proper functioning of the second hand arbor.

It is a common practice to provide a pressure spring to the second hand arbor for exerting a resilient pressure thereupon, so as to obviate an irregular movement of the arbor caused by the unavoidable backlash appearing in the related gearing, especially when the arbor is fitted in the center second type timepiece. In this way, a pressurized sliding contact is realized between the pressure spring and the arbor, and between the latter and its bearing means.

It is the main object of the present invention to provide a positioning means capable of obviating various conventional drawbacks to be described, efiicient in its function, simple in its design and easy to fit.

This and further objects, features and advantages of the invention will become more apparent when read the following detailed description of several preferred embodiments of the invention in comparison with prior art.

In the drawings:

FIG. 1 is a plan view of a conventional pressure spring.

FIG. 2 is a plan view of a conventional positioner for a slightly modified pressure spring from that shown in FIG. 1.

FIG. 3 is a sectional view of the spring positioner shown in FIG. 2, the section being taken along a section line 3-3 shown therein.

FIG. 4 is an exploded perspective view of a preferred embodiment of the invention.

FIG. 5 is a longitudinal sectional view of the pressure spring positioner assembly shown in its exploded view in FIG. 4.

FIG. 6 is a substantially similar view to FIG. 5, showing, however, several main constituent parts of a preferred second embodiment of the invention.

FIG. 7 is a perspective view of a third preferred embodiment of the invention.

FIG. 8 is a perspective view of a modified pressure spring employable in the present invention.

As a preparatory description, two preferred embodiments of comparative conventional pressure spring positioner will be explained briefly by reference to FIGS. 1-3.

In FIG. 1, illustrative of the first embodiment of conventional pressure spring, generally denoted by the numeral 10, the base end 11 of this spring '10 is formed into a pair of lateral wings 11a and 11b rigidly united with each other, a bolt hole, not appearing on the drawing, being formed at the junction area of these wings and on an axial center line 12 of the spring 10.

From the said junction area, a spring stem 13 extends along said center line 1 2 said stem being formed at its free end with a fork 14 comprising a pair of arms 14a and 14b, a recess 15 being formed between and by these end arms for allowing free passage of second arbor 16. Each end of said lateral wings 11a and 11b, there is provided a positioning hole 17 or 18 for the insertion of positioning pin, although not shown.

For attaching the spring 10 at its base end 11 to a mounting plate which is a modified form from that shown at 21 in FIG. 2, a fixing screw 22 is inserted through the corresponding bolt hole. In this arrangement, for attaching the pressure spring to the mounting plate, a single bolt at 22 is utilized, and for theprevention of possible and unintentional pivoting movement of said pressure spring relative to the mounting plate and around said attaching bolt, the pair of positioning pins inserted through said openings 17 and 18 are utilized.

In the second embodiment shown in FIGS. 2P3, the pressure spring shown generally at 10', has a base end 11' having practically no lateral wings, yet being formed with a pair of straight side edges 11c and 11d, which are being positioned snugly in a corresponding recess 25 defined by a pair of straight edge walls 23a and 24a formed on a pair of projections 23 and 24 made integral with the mounting plate 21, the latter being detachably attached to a conventional plate, not shown, by means of a pair of fixing bolts. 19 and 20.

In these embodiments, it is a requisite demand in the art to avoid a lateral contact of the spring fork arms 14a, 14b and 14a, 14b with the second arbor 16 or 16'. If such lateral contact should be invited, a too much strong frictional force will be applied to the arbor which results in a disturbance in the proper functioning of the timepiece. Under extreme circumstances, the regular movement of the timepiece may be stopped.

In order to avoid such lateral contact between the pressure spring and the second hand ar-bor caused by unavoidable fabrication errors, it is necessary to select the distance between the positioning openings 17 and 18 in the case of the first embodiment. If such a counter measure should be employed, the overall dimensions of the pressure spring must be increased correspondingly. This means naturally a grave disadvantage, especially in the case of a smaller timepieces. An employment of a larger size pressure spring of the above kind provides, especially in the case of such timepieces as of rather complicated design, a considerable difficulty in the fitting of the spring in position, resulting in a disadvantageous increase of the manufacturing costs of the timepiece.

In order to obviate disadvantageous fluctuations of the resilient pressure among a large number of pressure springs manufactured on an industrial scale, it is highly preferable to adopt a rather smaller spring constant and a larger value of spring deflection, thereby assuring a stabilized urging efiort exerted upon the second hand arbor in its longitudinal direction. The prior pressure spring used for this purpose is provided with none of such means for limiting the height of its free end as measured when the spring is in its free state kept in position. Therefore, when the second hand arbor and its bearing means are being assembled in position, the pressure spring which has been already fitted in position, is kept with its free end so high from its regular or working position that the arbor and the bearing means may be assembled in position in the timepiece movement only with considerable difficulty which leads in a substantial limitation in the freedom of choice of the design spring constant. As will appear from the following detailed description of the preferred embodiments of the invention, these conventional drawbacks may be completely obviated by the novel teaching of the invention.

Next, referring to FIGS. 5-7, a first embodiment of the invention will be described in detail.

In FIG. 4, the numeral 30 denotes a pressure spring which has a base end 31 shaped substantially in the same configuration with that at 11' appearing in the second conventional embodiment, said base end being formed with bolt hole 31a adapted for insertion of a set screw 32 similar to that shown at 22 or 22' in the foregoing. For attachment of the base end 31 onto a mounting plate 32 by means of said set screw 32', this plate is formed with a tapped hole 33 as shown. The plate 32 has a general configuration substantially similar to that shown at 21 in the foregoing, but, in the present embodiment, the plate is formed with no positioning projections such as shown at 23 and 24 in the foregoing. The mounting plate 32, is formed further with a pair of bolt holes 34 and 35 for receiving fixing bolts such as shown at 19 and 20 in the foregoing for attachment of the mounting plate to a conventional lower plate 36, the latter being shown in FIG. 6, but the bolted connections have been omitted therefrom on account of their popularity.

The pressure spring comprises a spring stem 37 similar to that shown 13 and 13 in the foregoing, said stem being formed with a forked end comprising a fork arms 38a and 38b and an elongated axial recess 39. The length of the fork arms 38a and 38b is selected to a considerably longer value than the conventional corresponding arms such as at 14a and 14b, respectively, in the foregoing. The length may preferably be a double or more of the conventional.

The mounting plate 32 is formed further two openings 40 and 41 in proximity to a rounded apex 32a, the former opening 40 being larger than the latter 41 for free passage of a conventional second hand arbor which is similar to that shown at 16 or 16' in the foregoing. The plate 21 or so shown in the foregoing is naturally formed with a similar opening as at 40 for the same purpose, although not specifically shown in FIGS. 1 and 2 on account of its popularity.

The latter opening 41 is designed and arranged for receiving a stop pin means formed into a tapered and headed pin 42 comprising an enlarged head part 4201, an upper cylindrical part 4212, an intermediate taper part 420 and a lower and reduced cylindrical part 42d. The reception opening 41 has such dimensions that it receives snugly said lower and reduced cylindrical part 42d, as appearing in FIGS. 5 and 6.

When the pressure spring is fitted in position, the mounting plate 32 is attached fixedly to the lower plate 36 by inserting set screws, not shown, into the respective bolt holes 34 and 35 and turning them in their screwing direction. The lower plate 36 is formed with corresponding tapped openings for receiving threaded parts of these screws, .although not shown on account of very popularity thereof.

Then, the base end 31 of the pressure spring 36 is attached to the mounting plate 32 by inserting set screw through bolt hole 31a into tapped hole 33 and turning it in its screwing direction. With progress of the screwing, the free part of the spring comprising a substantial part of spring stem 37 together with the forked free end of the spring will rise up by its own resiliency. The final risen-up position of the free part of the spring 30, having been attained upon tight screwing of set screw 32, is shown at 30' in FIG. 5. In practice, such a substantial rise-up of the springy free part of the pressure spring 30 must be, however, prevented on account of the thereby caused difficulty of the assembly work of the second hand arbor 42. 1

In fact, therefore, the stop pin 42 is passed at first through the recess 39 and then it is brought into position in the reception opening 41, and finally the spring base end 31 is fixed onto the base plate 32 in the above-mentioned way. The width of recess 39 is so selected for allowing a free passage of the stern part of the stop pin 42, comprising the parts 42b, 42c and 42d. Therefore, an excess spring-up on the forked end 38 of the pressure spring 30 is effectively prevented by pressure contact of the forked end with the enlarged head part 42a of the spring. During screwing attachment of the spring base end 31, by means of set screw 32', the spring 30 is subjected to a turning movement. But, such turning movement of the spring 30 is positively prevented by strong pressure contact of the forked end 38 of the pressure spring 30 with the lower surface of the flange-shaped pin head 42a. This preventing effect will be further assured by the provision of said recess 39 which, by possible contact with the upper cylindrical part 42b, will prevent the aforementioned kind of disadvantageous pivotal movement of the pressure spring 30. Such pre-assembled position of the pressure spring is shown at 30 in FIG. 5.

In place of the preparatory attachment of the mounting plate 32 to the lower plate 36, it is more preferable for easier assembly of the related parts to the timepiece movement, to fit the afore-mentioned sub-assembly comprising: mounting plate 32, pressure spring 30, set screw 32 and stop pin 42 set in position, to the movement.

Anyhow, as a standard preparatory job, the second hand arbor 45 together with its pinion 45a fixed attached therewith is assembled in position in the timepiece movement, and more specifically relative to the upper plate 43 and the lower plate 36, and then the sub-assembly including the mounting plate and the pressure spring attached thereto in the aforementioned way is assembled into position, as shown in FIG. 6. In this case, when the pressure spring has been sprung up at a high position as at 30 in FIG. 5, the assembly job will become highly difficult and very much troublesome, when following after the prior art.

On the contrary thereto, the sub-assembly as assembled according to the inventive teaching has the positioning and deflection-limiting stop 42 held in position relative to the pressure spring and the mounting plate, the aforementioned conventional drawback can be positively obviated.

When the arbor 45 and the sub-assembly have been fitted in position as shown in FIG. 6, the pinion 45a acts upon the pressure spring so as to lower the spring a small distance from the sub-assembled position sown in FIG. 5 at 30" to position 30" in FIG. 6. Thus the forked end 38 is physically separated from the lower surface of the flanged head 42a of the positioner 42 and the lower surface of pinion 45a is brought into and kept in pressure engagement on an intermediate point of the spring stem 37.

It will thus be seen from the foregoing that the provision of the positioner pin 42 does not influence in any way upon the regular working pressure exerted upon the second hand arbor 45 by the pressure spring 30, thus no pressure fluctuation being encountered.

Thanks to the provision of tapered part 420 on the positioner pin 42, the side edges defining the recess 39 do not regularly contact with the pin 42, thus otherwise possible fluctuation of the axial pressure exerted by the pressure spring upon the second hand arbor can effectively be obviated.

In the second embodiment shown in FIG. 7, similar parts as those in the foregoing first embodiment are shown with respective same reference numerals, yet each added with 100, for easy and simpler comparison.

In this second embodiment, a positioning pin is formed on the mounting plate 132 in close proximity of the arbor-reception opening 140 for limiting excess pivotal movement on the pressure spring 130 around the fixing screw 132. On the other hand, the upper plate 143 is formed with a recess 143a having an upper wall 143b defining partially the latter. The forked end 138 of the pressure spring 130 is additionally formed with a third arm 138c which is kept in pressure engagement with said upper wall 143b, thus latter acting as the spring pressure limiter shaped in the form of the enlarged pin head 42a in the foregoing first embodiment.

From the foregoing, the design and function of the present second embodiment of the positioning mechanism for the pressure spring. may be well understood without further detailed analysis.

The fixing arrangement for the spring base end 31 or 131 may be modified in various ways. As an example, the set screw 32 or 132 may be in the form of a stepped screw so as not to press the spring base end against the upper surface of the plate 32 or 132 and then the pivotal limitation for the pressure spring may be taken up by the upper cylindrical part 42b of the pin 42. In this way, a possible damage on the spring base end, as may be encountered during fixation of the set screws 32' or 132 may be avoided.

In FIG. 8, a modified form of the pressure spring is shown. In this figure, all the reference numerals are shown same as in the first embodiment of the invention, yet added each with 200.

In this modification, the spring base end 232 has been shaped into a hook havinga recess 232a. The adoption of this measure will assure a more easy attachment and detachment of the pressure spring 230 to and from the mounting plate. For attachment of this base end 232, a stud pin may be used in place of a set screw as at 32' or 132.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A positioning mechanism for a pressure spring se cured at one end to a stationary member of a timepiece movement with the spring normally kept in resilient pressure contact with a portion of the second hand arbor of the timepiece for exerting a resilient axial force thereon comprising a pair of forked arms formed on the free end of said spring adjacent said arbor, positioning means secured to said stationary member and disposed to engage said forked arms to restrict movement of said spring when said spring is not engaged by said portion of said arbor, said forked arms normally being positioned out of engagement with said positioning means when disposed in resilient pressure contact with said portion of said arbor after assembly of said arbor in said timepiece.

2. A positioning mechanism as set forth in claim 1 wherein said positioning means comprises a pin having an enlarged head and a reduced stem, said pin being fixedly mounted on said stationary member with said pressure spring.

3. A positioning mechanism as set forth in claim 2, wherein said stem of said pin comprises an upper cylindrical part, an intermediate tapered part and a lower reduced cylindrical part, said upper part acting as a limiting means for preventing excess pivotal movement of said spring prior to the assembly of said arbor in said timepiece.

References Cited UNITED STATES PATENTS 943,890 12/1909 Prisant 58-140 1,976,181 10/1934 Marti 58-140 2,015,905 10/1935 Marti 58-140 2,456,071 12/1948 Marchand 58-440 3,408,810 11/1968 Meitinger 58-125 RICHARD B. WILKINSON, Primary Examiner S. A. WAL, Assistant Examiner 

